检测物体是否在摄像机范围内

// <summary>
/// 对bound来说，它有8个点，当它的8个点同时处于摄像机裁剪块上方/下方/前方/后方/左方/右方，那么该bound不与摄像机可视范围交叉
/// </summary>

public static class Expand
{
public static bool CheckBoundIsInCamera(this Bounds bound, Camera camera)//检测物体是否在摄像机范围内
{
System.Func<Vector4, int> ComputeOutCode = (projectionPos) =>
{
int _code = 0;
if (projectionPos.x < -projectionPos.w) _code |= 1;
if (projectionPos.x > projectionPos.w) _code |= 2;
if (projectionPos.y < -projectionPos.w) _code |= 4;
if (projectionPos.y > projectionPos.w) _code |= 8;
if (projectionPos.z < -projectionPos.w) _code |= 16;
if (projectionPos.z > projectionPos.w) _code |= 32;
return _code;
};

Vector4 worldPos = Vector4.one;
int code = 63;
for (int i = -1; i <= 1; i += 2)
{
for (int j = -1; j <= 1; j += 2)
{
for (int k = -1; k <= 1; k += 2)
{
worldPos.x = bound.center.x + i * bound.extents.x;
worldPos.y = bound.center.y + j * bound.extents.y;
worldPos.z = bound.center.z + k * bound.extents.z;

code &= ComputeOutCode(camera.projectionMatrix * camera.worldToCameraMatrix * worldPos);
}
}
}
return code == 0 ? true : false;
}
}